Pain

Question 1

Differentiate between two types of noicereceptors?

Answer 1

Aδ fibers mediate sharp, intense or first pain
Type 1: noxious mechanical
Type 2: noxious heat

C-fibres mediate dull, aching or second pain
Noxious thermal, mechanical and chemical stimuli

Question 2

What is the gate control theory?

Answer 2

That pain could be inhibited in the spinal cord before it reached the brain. We now know that activation of A-beta fibres can inhibit pain signals in the dorsal horn by activating inhibitory interneurons which block the signal transmitted by A-delta or C-fibres.

Question 3

What are the descending control pathways?

Answer 3

These pathways are the ways the CNS can control pain. These pathways can inhibit (i.e. descending noradrenergic pathways from the LC) and facilitate (i.e. descending serotonergic pathways from the RVM) nociceptive signalling the dorsal horn.

Question 4

Describe peripheral sensitisation?

Answer 4

Peripheral- Inflammatory mediators such as bradykinin, histamine etc. all bind to receptors and cause the properties of C-fibres to change (i.e. they have a lower activation threshold for painful stimuli which manifests as primary hyperalgesia).

Question 5

Describe central sensitisation?

Answer 5

On-going activation of c-fibers causes a form of NMDA receptor mediated synaptic plasticity. This causes changes in the central processing of adjacent A-delta fibres, which results in the spread of sensitivity away from the injury site on the skin

Question 6

Define allodynia?

Answer 6

Allodynia: pain due to a stimulus that does not normally provoke pain

Question 7

Define the two types of hyperalgesia?

Answer 7

Hyperalgesia: increased pain from a stimulus that normally provokes pain.
Primary- increased pain at site of stimulus
Secondary- spread of pain to adjacent areas to site of stimulus

Question 8

What are the changes that occur to pain modulation in chronic pain?

Answer 8

During chronic pain there are changes in descending control systems. Descending noradrenergic pathways are protective and loss of this control is associated with the development of chronic pain. Similarly, there is a shift towards descending facilitation in chronic pain patients.

Question 9

What is condition pain modulation?

Answer 9

Condition pain modulation it is possible to measure how efficient the descending inhibition is in a patient.

Question 10

What is neuromodulation?

Answer 10

Neuromodulation is a novel way by which to reduce chronic pain symptoms in patients without using drugs. They are thought to activate areas of the brain involved in pain control such as the descending control systems